Hydraulic power steering mechanism



May 19, 1953 H. w. ROCKWELL 2,638,993

I HYDRAULIC POWER STEERING MECHANISM Filed Sept. 21, 1950 3 Sheets-Sheet2 INVENTOR. flA/zm M foe/(wax.

H. w. ROCKWELL HYDRAULIC POWER STEERING MECHANISM May 19, 1953 5Sheets-Sheet 5 Filed Sept. 21, 1950 "INVENTORY. fil al/5y M Poem/44,

Patented May 19, 1953 UNITED STATES rsreu'r o-rrice HYDRAULIC POWERSTEERING MECHANISM Harvey W. Rockwell, Cedar-.Rapids, Iowa, as

Signor, by .mesne assignments,.-to AllisChalmers Manufacturingcompany, acorporation of Delaware Application September 21; 1'195Q5fSfiFi2L1N0-1186;,043 9Claims. (cuss-#792) -My invention relates to mechanisms forsteering vehicles and is especially concerned-with a structurefor-steering vehicles of the off-highway or "earth-mover type usuallycomprising a two- ,wheel tractor articulated with a trailer about avertical pivot-axis at least. The tractorisnormally a rubber-tired,power-vehicleand-the trailor usually has twowheels disposed at somedistance fromthe pivot-axis and helping to support 7 some sort of earthcarrying structure such as a wagon or scraper.

Mechanism is provided for varying and holding the angular relativerotation of the vehicles aboutthevertical or fifth-wheel axis. Becauseofthe large size of the vehicles usuallyso constructed, it iscustomary-to effectuate the relative pivotal movementbetween the tractorand the trailer by power means such as a hydraulic actuator suitablyapplied :and controlled. It is also customaryto provide for transverseoscillation of the tractor with respect to the trailer, usually'about .alongitudinal, horizontal axis coplanar withthe steering pivotal axis.

Under many operating circumstances, all of the steering movementnecessary is a relatively small pivotal rotation between-the, tractorand trailer to either side of a central, norm-alposi- ,tion. Underothercircumstances-{it is highly advisable toafford a pivotal movementabout the vertical steering axis from a normal straightahead position toat least '90- degrees to either side, a total steering swing through ahalf circle or 180 degrees.

Various successful structures for this general I type of steering havebeen proposed and have been built but-mostof them are restricted tosteering angles much less than 90 degrees either side of center. Theproblem is sometimes met with a rotary hydraulic actuator, butit ispreferred to utilize linear hydraulic devices. A rep- 1 .resentativedevice of this sort is disclosed in Patent 2,362,262 toH. C.-French,issued November '7, 1944. Frenchs structure contains levers opoerated-by single-acting hydraulic jacks and connected by a flexiblechain toa sprocket onthe steered vehicle. This structure, thougheffective within its range-does not providea rugged and compact controlof large-angle steering motion --between the. tractor and the trailer.

It is therefore'anobgiect of my invention-to.

provide a steering mechanism effective to steer a tractor and trailerrelative to .each other through-an angle oi-approximately 90 degreeseither side of the straight-ahead, normal position..

A further object of the invention isto provide such a steering mechanismincorporating hy- .draulic. steerin lacks. of theilinear type.

Astillflfurther object of the invention is to providaior safety and formanufacturing economy, asteeringmechanism in duplicate halves, eitheralone being effective, thoughwith reduced power, fully tosteer thetractor-trailer combination.

Another object of my inventionis to ,provide double acting .1 acks and.appropriate connections so that both a pulling and a pushing effort canbe, realizedto rcsultli'n reasonably uniform, turning effortthroughllBrO degrees from linear jacks. Another. objector, my inventionisto relate the steering mechanism with the pivot mechanism of thetractor and trailer so that the. clearances between the moving parts areadequate even though steering is efiectuated through wide I angleseither side of center.

A still'further objectis to provide an improved steering mechanism Otherobjects, together with the foregoing, are

attainedin-the.embodiment of the invention described in'theaccompanying.description and disclosed in'the accompanying drawings inwhich Figure 'lis'ai plan of thexsteering mechanism :of my invention andsome adjacent parts shown "in full lines, a typical tractor and part ofa trailthe .ipl'anes of section being indicated by the 'lines'33 ofFigure 1.

"Figureflis a crosssection on the plane 5- 4 of FigureZ showing'in fulllines the orientation ofithe. steering'mech-anism for a turn ofapproximately'QO.degreesiin one direction and showing in'brokenilinesthe orientationof the structure iior steering straight, ahead.

"While the steering, mechanism. of myinvention is readily embodied in,a, number of different forms and. is subject tovariations depending uponthe particular environment. in which, it is utilized, it hassuccessfullybeen incorporated in a vehicle combination, in which atractor. t isutilizedlwith j-a trailer f1. The, trailer is illustrated as part. of

an earthmover ofa standard kind; for example,

passhownin thepatentto Choateand Austin '2;347;882; i.S-S 11edMay'2,I944.

"T'nejtrailerincludes a transverse yoke t and a (pair ofvehiclcsupportina rear .wheels.,. not shown,

having their rotational axis spaced behind and parallel to thetransverse yoke 8. The trailer extends upwardly and forwardly from theyoke in a gooseneck 9 and terminates in the vicinity of a vertical axisHi. This is the common line about which the trailer 1 and the tractor 6are considered to turn for steering. The tractor includes a source ofpower located under a hood I and effective to drive a pair of groundengaging wheels l2 and IS. The front wheel rotational axis I4 is aheadof the axis In and is parallel to the axis of the rear Wheels when thevehicle is going straight ahead on the level. At a station I5 for thevehicle operator, a steering wheel H5 is provided so that the operatorcan manipulate the steering mechanism. Usually such mechanism is drivenfrom the source of power under the hood II and includes a hydraulicreservoir, pumpin and valving arrangement, not shown, connected to thewheel IS.

The tractor 6 has a main frame H in its rearward portion behind thewheels I2 and I3 including a sleeve l8 encompassing a longitudinallydisposed horizontal tilt axis I9. The axis |9 is preferably in themedian plane of the tractor at right angles to the rotational axis l4 ofthe wheels l2 and I3.

Coincident with the axis I9 is a shaft 20 extending from the sleeve l8and held firmly against longitudinal relative motion on a subframe 2|.The subframe is substantially an elongated, flat box upswept andbroadened at its rearward end and at its forward end enlarged into adrum 22. This serves as the base for a pivot pin 23 upstanding from thesubframe approximately on its median line 24 and encompassing thevertical axis IU which intersects the tilt axis l9. Such intersection iscustomarily, although not necessarily, at a right angle. The pivot pin23, with suitable bearings, forms a journal support for a pivot housing26 encompassing the pin 23 and pivotally related to the subframe 2|.Suitable ends 21 and 28 on the pivot housing confine it againstvertical, axial motion. The forward portion of the gooseneck 9 mergeswith the pivot housing 26 and incorporates it in the frame 8 of thetrailer as one structure. By this interconnection the trailer and thetractor rotate about the axis ID for steering even though the trailer,the su'bframe 2| and the steering mechanism in part rotate about thelongitudinal tilt 7 axis l9 in a side to side oscillation.

To establish and confine the relative pivotal steering motion of thetractor and trailer about the axis ID to the angularity desired by theoperator, I provide on the subframe 2| similar or duplicate structureson opposite sides of the center line 24 arranged as mirror images on thelefthand and on the right-hand sides in straight ahead position. Theupswept rear part of the subframe at one side provides a pair of ears 3|and 32 straddling a tongue 33 at the rear end of a double acting,hydraulically expansible chamber structure 34. A pivot interconnectionis effectuated by a pin 36.

The structure 34 includes a cylinder from which projects a piston rod31. A piston 38 is on one end of the piston rod and at its other end thepiston rod is pivoted by a pin 39 to an intermediate portion of anarcuate, multiplying lever 4|. This lever is constructed for symmetry ininverted positions and includes an upper plate 42 and a lower plate 43between which the piston rod 31 is freely operative. At its fulcrum, the

- multiplying lever 4| is constructed with an offs t axial enlargement44 and is journalled at spaced points on a mounting pin 46 upstandingfrom an enlargement 4'! firmly fixed in the subframe. In the normal,straight ahead position of the parts, the pin 46 is disposed immediatelybehind the steering axis i0 and below the gooseneck 9.

The opposite end of the multiplying lever straddles the normallyrearward end of a strut 48 to which it is connected by a pivot pin 49.The term strut refers to a member which both pushes and pulls. The otherend of the strut is connected by a pivot pin 5| to upper and lowerplates 52 and 53 of a bracket extension 54 extending forwardly from andfixedly secured to the housing 26 on the side thereof opposite thegooseneck 9. A central stop 56 on the bracket 54 engages side stops 51and 58 on the subframe to limit the extremes of steering movement.

A quite similar structure is provided on the opposite side of thesubframe 2|. A duplicate, double acting hydraulically expansiblemechanism 6| is connected by a pivot pin 62 at one end to the ears 3|and 32 on the subframe. At its other end the expansible mechanism has apiston rod 63 joined by a pin 54 to a second, arcuate, multiplying lever66. This has substantially the same construction asthe first lever 4|and is similarly provided with an offset.

When both levers are assembled on the fulcrum pin 46, they interleave toprovide a mutually straddled mounting, there being appropriate bearings61 disposed in them to reduce the turnpin TI to one end of a strut 12identical with the strut 48. The other end of the strut 72 is joined bya pin 13 to the extension bracket 54, the connection being between theupper and lower plates 53 asnld 52 in mirror symmetry with the mountingpin Each of the linear cylinders 34 and 6| is provided at opposite endswith hydraulic connectors, not shown, leading to a standard valvecontrolling flow of hydraulic fluid under pressure from a driving pumpand to a reservoir. The valve is also usually effective in one positionto lock the fluid within the hydraulically expansible chambers withoutinflow or outflow in order to hold the steering mechanism rigidly in aselected posi- 1011.

The oscillation or lateral tilting of the tractor and trailer areaccomplished in the normal way and the relative steering or pivotalmovement of the tractor and trailer take place in a normal way about thesteering axis IE but the amount of steering or the angle of steering ismuch greater than is usual with power devices, When one of the jacks 34,for example, is provided with steering fluid under pressurein itsrearmost portion, it is effective to expel the piston rod 31. This inturn oscillates the multiplier lever 4| about the fulcrum pin 46. Sincethe strut 39 is connected at a radially more remote point, the strut ismoved an even greater amount in compression. The strut also moves in adiiferent direction than the linear piston rod due to the differentrelative locations of the pins 49 and 5| at different parts of theturning cycle. structure even alone affords an appropriate relativerotation between the trailer and the tractor.

:aesspcs H The iocatioirot' 'therfiiicrumipnriflirwitnirespect to tnesteering axis zmuandstheilc'cationsior the 1 3-9, and iliarei'suchvthaminzieirectz the arcuate multiplying leverrn andftheistrutzrm considered :together, .ipartialry rrencompass :the steeringhousing 26 when large or :maximum 'turnsare made. A line 16drawnthroughfthe center of the pin 46 and the-center :oii'the tpinzillpasses from one sid'e 'of the st'eeri-ng 'axis 1 .-'to the other.

'Steeringmotion in one direction. isefiectuated by a compressive stressin the-pistonirodit and in 'the strut 48. *By a reversal of thehydraulic"connectionsto' the cylinder- 3 d to exert" pressure onthe' forward endof the piston, t'he1piston rod 3 T isplaced intension and is 'Iwithdrawninto the :cylinder 36 thus "rocking thearcuate lever 31min I the reversedirection and by ten'sioningthe strut 08 'causes the opposite steering"rotation between ithe tractor and the trailer. It isfthusxpossible byopposite senses of'motionofthe hydraulic cylinder, to provide steeringof the. vehicle thr'oughout'QO degrees from straight ahead: position toone side and throughout QO 'degrees from straight aheadposition to theother side. All or cylinder '34. The positions of the-parts-fora-QOdegree turnin one directio-n are shown in full 1 lines in Figure 4' anda mirror image represents "the position of the parts for afull 90degree" turn 1 in the opposite direction" from straight ahead p0 sition,illustrated by broken lines in Figure 4. The mechanical advantagesorleverages of the two duplicate system's complement each other sinceone system is strong when the other is weak, and vice ve'rsa.

As distinguished-fromsome pi ioripractice, double acting cylinders areutilized so that asingle one of them can suifice and' sol that bothpushing forces and pulling forces maybe utilized foroomplete 90 degreesteering in either direction. As further distinguished from priorpractice, there is employed herein a strut which is effective totransmit motion in two opposite directions, both by tension and bycompression. The point (for example, 49) of attachment of a strut to thepivot housing 2%, from the vantage of the subframe 2 l, in effecttravels around the steering axis [0 While the strut itself (for example,48) occupies a position other than tangential throughout much of itsmotion. It is therefore possible to transmit force around a corner, soto speak, from the hydraulic cylinder not only in tension but also incom pression. By the provision of double acting hydraulic cylindersoperating on arcuate levers con nected by struts to the bracketextension, all 65 mounted and disposed and located as disclosed, thetractor and trailer are connected for steering at least 90 degrees inone direction from normal and conversely, a. complete 90 degree turn inthe opposite direction from normal. All the while the steering is undercomplete hydraulic control and is hydraulically locked in both tensionand compression in any selected position for safety.

What is claimed is:

1. A steering mechanism for a tractor and a 25 "tion of said Y, tractorfor r'el'ativ 6 trailer.comprising a irrame, means for- 'conne'ctingsaisd rramerto' tbe rearwardportinn of'nsaid trac- -tcr-1for transverseatiltingsaboiit 'longitudinal central axis, a pivotllpin on tramefhavin'g :a substantiallysverticaisaxis m terseetingeaid lon- -gitudinal--'axisxlneari* thezcenter :said Tframe, a pivot "housing Journaledx-onnsaid pivot. :pin "and interconnectedwiththel traifenrafulcrwn pinon frame bclirind said pivotrqain aiminga 10 substantially verticalaxis. intersecting rsa'idlongi- -"=2o-other "end df said -strutswandsaid extension br'acket,

2. A steering mechanism for a tractoie e mdsra trailercomprising a:" name,aa longitudinal pivot '-ior -connecting said frame tozthe-ream'wardmon "ing about a longitudinal central:.-axis,.lamivotsf-pin "on said "frasrie"having a, substantiallywent'roal ers'ecting said:longitudinalfiaxisoneaxxthe eenterofbsaidframeya pivot housing iomnaled 1 on said pivot pin and interconnected iwithithe trailer; a fulcrum ipinnonrsaid lframeiabehind :said ivot pinand having aisi'ibstantiallywerticalliaxis intersecting s 'said 1longitudinal axis, i levers :iourn'aled at-their inner *ends tonzsaid'fulcrnmrqziin inthe reversesense with the operationnfthe em -andextendingin'sopposite:directions: therefrom,

each of'said zlevers benig curvedto extendiamund said' pivothousing-eaapair .zof double :actinaidhil- --dranlic jacks each being.t-atrone rend" mounted on the rearward part or saidflrame behindxsaidvot pin aud- 21 the other -'endsengagingi an termediate ipa'rt' o'f *oneofisaidlleverstzan extension bracket on thexforward-epartxofsai'dt-pivot hou'sing .=aheadfof said:ipivotpingazipaiiroffiftransverse'ly--=spacedpivot connections on said hou'sing ahead ofsaid-pi-votpin, and a pairsfofzstrots con -verging in a forwarddire'oti'on, each of said *struts at one ei-id engaging-' the outer endoof:safdlevers and-' he other end engaging a respective one-of sap-ivotconnections.

3. A steering mechanism for a .-ltract'or and a trailer-comprising -iarrame; means for connecting said frame to said tractor to pivot about alongitudinal horizontal axis, a pivot pin upstanding from said frame, apivot housing journaled on said pivot pin and connected to said trailer,

a pair of levers pivoted to said frame about an axis on one side of saidpivot pin, struts pivoted to and extending from the ends of said levers,

pivot connections between the struts and said housing on the other sideof said pivot pin, and a pair of double acting hydraulic jacks pivotallyconnected at one end to said frame and at the other end to said leversintermediate the ends thereof.

4. A steering mechanism for a tractor and a. trailer comprising a frame,means for connecting said frame and said tractor, a pivot pin upstandingfrom said frame, a pivot housing journaled on said pivot pin andconnected to said trailer, a lever at one end pivoted to said framebehind said pivot pin, a strut pivoted to said lever at the other endthereof, a pivot connection between said strut and said pivot housingforward of said pivot pin, and a double-acting hydraulic jack pivotallyconnected at one end "transverse tiltone to said frame and at the otherend to said lever between the pivot connections to said frame and saidstrut whereby said strut and lever may jackknife around said housing.

5. Asteering mechanism for a tractor and a trailer comprising a frame, apivot pin upstanding from said frame, a pivot housing journaled on saidpin, an extension bracket secured to and in the straight ahead positionbeing on the central forward part of said pivot housing, a fulcrum pinsecured to andin the straight ahead position being on the centralrearward part of said frame, levers mounted on said fulcrum pin andextending outwardly therefrom beyond said pivot housing with radii suchthat circles scribed by said radii would enclose the axis of said pivotpin, hydraulic jacks connected at one end to said levers and at theother end to said frame,

struts connected to said levers, and pivot connections between saidstruts and said extension bracket at points spaced transversely of saidbracket;

6. A steering mechanism-for a tractor and a trailer comprising a frame,means for connecting said frame to said tractor, a pivot pin upsaidhousing on the other side of said pivot pin from said first pivotconnection, an end of said strut being pivoted on said second pivotconnection, said pivot connections being located in such proximity tosaid pivot pin so that said lever, said strut and a line connecting saidfirst and second pivot connections triangularly encompass the axis ofsaid pivot pin when said trailer executes a 90 turn, and a hydraulicjack pivotally connected at one end to said frame and at the other endto said lever.

7. In a steering mechanism for a tractor and a trailer comprising aframe, a pivot pin upstand- 4 ing from said frame, a pivot housingjournaled on said'pin and connected to said trailer, the

combination of: a first lever connected at one end to said frame, asecond lever connected at one end to' said housing, the free ends ofsaid levers being pivotally interconnected, said levers comprising alinkage having substantially a V- :configuration which in all positionsof said tractor and saidtrailer encloses a maximum angle of no more thanapproximately and a hydraulic jack connected at one end to said frameand at the other end to one lever in said linkage.

8. A steering mechanism for a tractor and a trailer comprising a firstelement including a frame, and a first pivot member upstanding from saidframe; a second element including a second pivot member journaled withrespect to said first pivot member, and a connection between said secondpivot member and said trailer; means for connecting said first elementto said tractor to pivot about a longitudinal horizontal axis; a pair oflevers pivoted to one of said elements about an axis on one side of saidpivot members; struts pivoted to and extending from the ends of saidlevers; pivot connections between the struts and the other of saidelements on the other side of said pivot members; and a pair of doubleacting hydraulic jacks pivotally connected at one end to said one ofsaid elements and at the other end to said levers intermediate the endsthereof.

9. A steering mechanism for a tractor and a trailer comprising a firstelement including a frame, and a first pivot member upstanding from saidframe; a second element including a second pivot member journaled withrespect to said first pivot member, and a connection between said secondpivot member and said trailer; means for connecting said first elementand said tractor; a lever at one end pivoted to one of said elementsbehind said pivot members; a strut pivoted to said lever at the otherend thereof; a pivot connection between said strut and the other of saidelements forward of said pivot members; and a double acting hydraulicjack pivotally connected at one end to said one of said elements and atthe other end to said lever between the pivot connection to said one ofsaid elements and said strut whereby said strut and said lever mayjackknife around said pivot members.

HARVEY W. ROCKWELL.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,362,262 French Nov. '7, 1944 2,519,742 Collender Aug. 22,1950

